Comparison of functional and morphologic characteristics of mice models of noise-induced hearing loss

Objectives

This study was conducted to compare morphologic and audiologic changes after noise exposure in two different strains of mice (CBA and C57) and to create morphologically proven models of noise-induced hearing loss.

Methods

Mice were exposed to white noise at 110-dB sound-pressure level for 60 minutes at the age of 1 month. Hearing thresholds and outer hair cell functions were evaluated by auditory brainstem response recordings and distortion product otoacoustic emission immediately and 22 days after noise exposure. Cochlear pathology was observed and compared by light and electron microscopic studies.

Results

Both mice strains showed hearing threshold shifts with decreased outer hair cell function immediately and 22 days after noise exposure. More severe auditory brainstem response threshold shifts were observed in C57 mice compared with CBA mice at click, 8-, 16-, and 32-kHz tone-burst stimuli. A cochlear morphologic study demonstrated predominant outer hair cell degeneration at all turns of the cochlea; degeneration was most severe at the basal turn in both mice strains. A scanning electron microscopic study revealed more severe ultrastructural damage of outer hair cells at each turn of the cochlea in C57 mice. The lateral wall of the cochlea was more severely degenerated in CBA mice.

Conclusion

Both mice strains showed consistent, permanent noise-induced hearing loss with different susceptibilities and site vulnerabilities. Further studies to investigate the mechanism of the different degree and cochlear site vulnerability to noise exposure between two mice strains are necessary.     

Evaluation of cortical processing of language by use of positron emission tomography in hearing loss children with congenital cytomegalovirus infection

Objective

To predict cochlear implant efficacy and investigate the cortical processing of the visual component of language in profoundly deafened patients with asymptomatic congenital cytomegalovirus (CMV) infection.

Methods and cases

The cortical activity of two children with CMV-related hearing loss was evaluated with fluorodeoxyglucose-positron emission tomography (FDG-PET) with a visual language task before cochlear implantation. Total development and auditory perception ability were assessed one year after implantation.

Results

The two children with CMV-related hearing loss showed activation in the auditory association area where no activation was found in the controls, and exhibited nearly identical cortical activation patterns to those seen in patients with profound congenital hearing loss. In contrast, differences in total development in verbal ability and discrimination of sentences between the two cases were revealed one year after implantation.

Conclusion

These results might indicate that the differences of cortical activities according to hearing abilities could have been influenced by CMV infection that involves higher function of the brain directly and/or affects the cochlea peripherally. Additionally, if CMV infection might have affected only the cochlea, these cortical activation patterns were influenced secondary by the time course of hearing loss characterized by CMV infection, which had varied manifestations.Accurate diagnosis and cochlear implantation at the appropriate time are important for successful speech development, and each patient needs a personalized habilitation program based on their etiology and brain function.     

Medical ozone therapy for the inner ear acoustic trauma

Objectives

The goal of the study was to look at the potential protective effect of ozone therapy by studying its antioxidant and vasodilatation effects against hearing loss caused by acoustic trauma.

Methods

Thirty-two male Wistar Albino rats were divided into four groups of eight. The 1st group was exposed to acoustic trauma, the 2nd group was treated with ozone initially, and was exposed to acoustic trauma 24 h later, the 3rd group received ozone without trauma, while the 4th group was the control group. The 1st and 2nd groups were exposed to acoustic trauma with 105 dB SPL white band noise for 4 h. DPOAE and ABR tests were conducted in all groups on the 1st, 5th, and 10th days after trauma.

Results

In the 1st group, the effects of acoustic trauma continued on days 1, 5 and 10. The 2nd group's DPOAE and ABR results on days 5 and 10 showed significant improvement at all frequencies compared to deterioration on day 1, and the readings were comparable to baseline measurements.

Conclusion

Acoustic trauma is a pathology that is experienced frequently and leads to many problems in terms of health and cost. Ozone was demonstrated to be a reparative substance against acoustic trauma and, in addition, it can be supplied and applied easily.     

Evidence for genotype–phenotype correlation for OTOF mutations

Objectives

The aim of this study is to evaluate the auditory phenotype in subjects with OTOF gene mutations to describe genotype–phenotype correlations.

Methods

Twenty-two affected members from three families with homozygous OTOF mutations were included. Nine subjects were evaluated audiologically with otoscopic examination, pure-tone audiometry, tympanometry with acoustic reflex testing, auditory brain stem responses, and otoacoustic emission tests.

Results

Homozygous c.4718T>C (p.Ile1573Thr) mutation was associated with the auditory neuropathy/auditory dys-synchrony (AN/AD) phenotype and with progressive sensorineural hearing loss in four siblings in one family, while homozygous c.4467dupC (p.I1490HfsX19) was associated with severe to profound sensorineural hearing loss without AN/AD in four relatives in another family. Homozygous c.1958delC (p.Pro653LeufsX13) mutation was associated with moderate sensorineural hearing loss without AN/AD in one affected person in an additional family.

Conclusions

The audiological phenotype associated with different OTOF mutations appears to be consistently different suggesting the presence of a genotype–phenotype correlation.     

Hearing loss in vestibular schwannomas: analysis of cochlear function by means of distortion-product otoacoustic emissions

Objective

We investigated cochlear function in a group of patients affected by vestibular schwannoma (VS), by means of recording distortion-product otoacoustic emissions (DPOAEs).

Methods

Between January 1996 and January 2007, we observed 183 patients affected by unilateral VS. DPOAEs, compared to the corresponding hearing thresholds, were subjectively classified into three categories: “compatible” with hearing function, “cochlear” and “retro-cochlear”. We also related the responses to some clinical variables (tumor size, intracanalicular tumor and radiologic appearance of the internal auditory canal). Statistical analysis was performed.

Results

In 137 cases (74.9%), DPOAEs were as expected based on audiometry responses, while in 11 patients (6%) a “cochlear” DP-gram was recorded and in 35 patients (19.1%) DPOAEs evidenced a “retro-cochlear” pattern. In eight cases we detected acoustic responses despite a profound hearing loss. No statistically significant data merged from the comparison between “cochlear” and “retro-cochlear” responses and the clinical variables.

Conclusion

Our results confirm that sensorineural hearing loss due to VS can be of sensory and/or neural origin. DPOAEs still remain just a complementary auditory test; nevertheless, in case of severe or profound unilateral hearing loss, recorded acoustic responses may be suspicious for the presence of a vestibular schwannoma.     

Non-organic hearing loss in Chinese teenagers

Objective

To heighten the physician's awareness of non-organic hearing loss in teenagers in China.

Methods

Retrospective cases review of seven patients (six girls and one boy) with sudden hearing loss was conducted.

Results

Five patients presented with hearing loss bilaterally and two patients unilaterally. All patients suffered from severe to profound hearing loss. However, the acoustic reflex test indicated direct and indirect responses were present bilaterally at 1000 Hz 100 dB SPL. The results of ABR test revealed hearing threshold within 20–30 dB nHL. Further investigations indicated non-organic hearing loss was associated with school stress or environment conflict. Satisfactory outcomes were achieved in all patients.

Conclusion

Non-organic hearing loss should be considered when teenagers present with severe to profound sudden hearing loss if the acoustic reflex is present. School and home stresses are associated with the occurrence of non-organic hearing loss in the present study.     

The effect of caffeine on hearing in a guinea pig model of acoustic trauma

Objective

Caffeine is a widely consumed substance affecting the metabolism of adenosine and cellular metabolism of calcium. Noise also affects these metabolic pathways while inducing hearing loss. The aim of this study was to determine the effect of daily intake of caffeine on hearing loss after an episode of acoustic trauma in guinea pigs.

Materials and methods

In this pilot study, forty guinea pigs were randomly divided into four groups: group I (control, n = 10) received intraperitoneal saline, group II (n = 10) received intraperitoneal caffeine (120 mg/kg/day) for 14 days, group III (n = 10) was exposed to noise (tone of 6 kHz at 120 dB for one hour) and group IV (n = 10) was exposed to noise as group III and received caffeine as group II. Auditory brainstem responses were measured at four different frequencies (8, 16, 20, and 25 kHz) prior to and at intervals of 1 h, 3 days, 10 days, and 14 days after the initial treatment. On day 14, morphological analysis was performed to assess the effects of caffeine on acoustic trauma.

Results

Aggravated hearing loss was observed in group IV after 10 days of follow-up. After 14 days, one of the four frequencies (8 kHz) tested showed statistically significant greater impairment in hearing (8.2 ± 3.6 dB, p = 0.026). Auditory hair cells showed no difference while spiral ganglion cell counts were diminished in group IV (p < 0.05).

Conclusion

These findings indicate that caffeine may have a detrimental effect on hearing recovery after a single event of acoustic trauma.     

Prostaglandin E receptor subtype EP4 agonist serves better to protect cochlea than prostaglandin E1

Objective

The present study aimed to examine whether an E-prostanoid receptor 4 (EP4) agonist has superior protective effects to those of prostaglandin E1 (PGE1) in a guinea pig model of noise trauma.

Methods

Drugs were locally applied on the round window membrane of guinea pig cochleae, followed by exposure of the test animals to intense noise. Protective effects mediated by an EP4 agonist were compared with those mediated by PGE1. Auditory function was monitored by measurements of the auditory brainstem response (ABR), and histological damage was assessed by immunohistochemical analysis of cochlear specimens.

Results

Animals treated with an EP4 agonist exhibited significantly better hearing recovery than those pretreated with PGE1. Histologically, the numbers of remaining outer hair cells in cochleae treated with the EP4 agonist were significantly higher than in those treated with PGE1.

Conclusion

The selective activation of EP4 has a stronger protective effect on cochleae against noise trauma than does the broad activation of EPs by PGE1.     

Keratinic amyloidosis of the external auditory canal

Objective

We present a rare case of keratinic amyloidosis of the external auditory canal. This is only the seventh case reported of localized cutaneous amyloidosis of the external auditory canal with no systemic symptoms.

Patient

A 62-year-old man, who had complained of an itchy external auditory canal and left-side hearing loss, was referred to our hospital because of a bilateral external auditory canal mass.

Intervention

Biopsy of the external auditory canal mass suggested a diagnosis of amyloidosis. However, total systemic examination failed to identify any disease due to systemic amyloidosis. This led us to diagnose him with localized cutaneous amyloidosis of the external auditory canal.

Main outcome measure

We follow up periodically with systemic examination and local observation.

Results

Thirty months after the initial diagnosis, he remains in follow-up and has not shown any significant aggravation of the disease.

Conclusion

In previous cases, the chief complaints were itching sensations and pain in the external auditory canal as well as a sense of discomfort when wearing a hearing aid. This suggests that chronic stimulation and inflammation of the skin lining the external auditory canal induced amyloidosis.     

Simultaneous translabyrinthine removal of acoustic neuroma and cochlear implantation

Objectives

To report of a 65-year-old woman with bilateral Meniere's disease was referred for cochlear implantation (CI) due to severe/profound sensorineural hearing loss.

Methods

During the assessment workup, a vestibular schwannoma in the right ear was found by MR imaging. She underwent a translabyrinthine removal of the acoustic neuroma (AN) with sparing of the cochlear nerve and concurrent ipsilateral CI with a Nucleus Freedom device (Cochlear Ltd., Lane Cove, New South Wales, Australia).

Results

Complete removal of the AN was achieved without complications. Neural Response Telemetry (NRT) measurements, which showed poor morphology at the intraoperative tests, rapidly improved after activation, similarly to electrically evoked auditory brainstem responses (E-ABR). The patient reached 100% speech perception performances within 2 months from implantation, in the monaural condition. She was relieved from vertigo spell up to 14 months after the operation.

Conclusion

Cochlear implantation at the time of acoustic neuroma removal with VIII nerve sparing can be a safe and effective hearing restoration procedure.     

Evaluation of cochlear involvement by distortion product otoacoustic emission in Behçet's disease

Objective

The aim of this study was to investigate cochlear involvement in patients with Behçet's disease.

Materials and methods

Twenty-six Behçet's disease patients (52 ears) and 24 sex and age-matched healthy control subjects (48 ears) were included in the study. Pure-tone audiometry at frequencies 250, 500, 1000, 2000, 4000, 6000 Hz, immittance measures including tympanometry and acoustic reflex testing and DPOAE (distortion product otoacoustic emission) testing were performed in the patients and controls.

Results

A sensorineural hearing loss was found in eight patients (30.7%) as it was bilateral in five and unilateral in three patients. Although no typical audiometric configuration was found, one patient had a flat type audiogram, and the others had a high frequency hearing loss. The DPOAE responses of the patients and controls were significantly different in all frequencies (p < 0.05).

Conclusion

These results indicate that cochlea is affected by damage of outer hair cells in Behçet's disease.     

Bilateral secondary neurolymphomatosis of the internal auditory canal nerves: A case report

Background

Neurolymphomatosis describes the malignant lymphomatous infiltration of nerves.

Methods

We encountered a unique case of a 47-year-old patient with non-Hodgkin's lymphoma presenting with bilateral sensorineural hearing loss, vestibular dysfunction and bilateral facial nerve palsy.

Results

Magnetic resonance imaging demonstrated enhancement and thickening of internal auditory canal nerves bilaterally consistent with neurolymphomatosis. Patient was treated with combined intrathecal chemotherapy and total brain irradiation.

Conclusions

One must always remain vigilant for metastatic disease in patients with sensorineural hearing loss and/or vestibular dysfunction and facial nerve palsy in the context of known malignancy.     

Fully implantable hearing device with transducer on the round window as a treatment of mixed hearing loss

Objective

To demonstrate the safety and efficacy of the Otologics Carina Middle Ear Transducer for treatment of mixed hearing loss through a case report.

Methods

A Carina fully implantable device with the MET transducer for conductive applications was implanted in a 48-year-old woman suffering from right mixed hearing loss (mean PTA loss: 80 dB). A facial recess approach was used to access the middle ear. Sclerotic tissue obliterated the stapes footplate so the approach selected was to place the transducer directly on the round window. The mounting bracket was placed on the mastoid and the prosthesis was advanced toward the round window until the Otologics surgical software indicated contact. Effective stimulation of the cochlea was confirmed intraoperatively by ABR monitoring.

Results

Postoperative unaided PTA thresholds were unchanged after surgery. When the implant was activated, the mean PTA functional gain was 39 dB.

Discussion-conclusion

The capability of the Carina MET Ossicular stimulator to provide appropriate gain relative to the degree of hearing loss indicates that the device offers a viable treatment option for mixed hearing loss. However, these promising initial results establish the need for future work on two fronts: (1) further studies are needed including a greater number of patients to confirm these preliminary results; (2) a long term follow-up must be carried out to detect any possible cochlear adverse effects on the cochlea, in particular on the basilar membrane.     

The role of the medial olivocochlear system in the complaints of understanding speech in noisy environments by individuals with normal hearing

Objective

The aim of our study is to investigate the relationship between the complaint of speech understanding in noisy environments and the findings of contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise test methods in individuals with normal hearing.

Methods

Sixty-nine subjects between 18 and 53 years of age with normal hearing participated in the present study. The subjects were assigned to one of two groups, reported difficulty understanding speech in noise or no reported difficulty understanding speech in noise. After hearing and immitancemetric evaluation, contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise tests were administered to both groups. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.5, 2.0, 3.0 and 4.0 kHz.

Results

We found out that the speech recognition in noise scores and contralateral suppression values were lower in subjects with the complaint of speech understanding in noise than those who do not have such complaints.

Conclusions

We concluded that the complaint of speech understanding in noise may be related to the medial efferent system dysfunction, so central auditory nervous system.     

Inner ear pathology of alpha-galactosidase A deficient mice,a model of Fabry disease

Objective

Fabry disease is characterized by genetic alpha-galactosidase A deficiency, resulting in accumulation of glycolipids (GL-3) and tissue damage. Hearing loss is also common and attributed to GL-3 accumulation in the inner ear. The only reported histological studies dealt with murine and human specimens. Accordingly, histopathological studies of the cochlea were performed on an alpha-galactosidase A deficient murine model of Fabry disease, using C57BL6/J mice as the controls.

Methods

The hearing ability was evaluated using the ABR threshold, while cochlear specimens were observed light microscopically and ultrathin temporal bone sections by TEM.

Results

HE staining showed no accumulation of GL-3 or abnormal cochlear morphology in the alpha-galactosidase A deficient mice, but toluidine blue staining and TEM revealed GL-3 accumulation in the stria vascularis and kidney. No GL-3 accumulation was detected in the C57BL6/J controls by either HE staining or TEM. The alpha-galactosidase A deficient mice and the controls showed no clear differences in the ABR threshold (hearing acuity), but for older animals the threshold was higher in the C57BL6/J controls.

Conclusion

In summary, although the alpha-galactosidase A deficient mice showed no clear hearing loss, GL-3 accumulation was demonstrated in the cochlea.     

Peripheral hearing loss and auditory temporal ordering ability in children

Objective

The main objective of this study was to assess the influence of peripheral hearing loss (abnormal encoding of the auditory system) on auditory information processing. We examine the ability of children with and without hearing loss to correctly reproduce sequence blocks of acoustic stimuli that vary in type, number, and temporal ordering.

Methods

Twenty-six children between 8 and 12 years old, 13 with hearing loss and 13 without hearing loss, participated in the study. They performed an auditory temporal ordering task (auditory sequential organization task) by recalling two, three, and five verbal (/ba/-/da/and/a/-/da/) and nonverbal stimuli (acoustic transformation of /ba/-/da/) with a fixed interstimulus interval (ISI) of 425 ms. They also reproduced sequences of two elements with variables ISI, 20, and 1000 ms.

Results

Children with hearing loss had significantly lower correct responses than children with normal hearing for sequences of two, three, and five verbal stimuli with similar and complex acoustic features (/ba/-/da/), for an ISI of 425 ms. There was no significant difference in performance between children with hearing loss and their peers with normal hearing on nonverbal sequences or verbal sequences with different and complex acoustic features (/a/-/da/) when ISI was 425 ms. Furthermore, children with hearing loss performed significantly lower than their peers on the three groups of stimuli when ISI was 20 ms between two stimuli.

Conclusion

Peripheral hearing loss can influence auditory information processing in the central auditory system.     

Hearing loss in the shaken baby syndrome

Objectives

To evaluate hearing in children diagnosed with shaken baby syndrome.

Methods

A retrospective study conducted in a pediatric tertiary care center between 2006 and 2012. Children diagnosed with shaken baby syndrome were included for hearing evaluation by conventional audiometry, distortion product otoacoustic emissions and auditory brainstem responses.

Results

Twenty-eight children were included (22 boys and 6 girls). The mean age of children at presentation was 8 months (range 1–26 months) and the mean delay before audiometric evaluation was 30 months (range 1–87 months). One child was diagnosed as having a moderate sensorineural hearing loss. The tympanic membrane mobility was normal (type A) for both ears in 22 children, one child had a reduced tympanic mobility in one ear, two children had a negative pressure, one child had a functional trans-tympanic tube and test was not performed in 2 patients.

Conclusion

This is the first study reporting hearing loss as a possible result of shaken baby syndrome. However, further studies with larger number of children would be preferable. We recommend hearing evaluation for these children to rule out hearing loss.     

Brainstem auditory evoked potentials with the use of acoustic clicks and complex verbal sounds in young adults with learning disabilities

Purpose and background

Acoustic signals are transmitted through the external and middle ear mechanically to the cochlea where they are transduced into electrical impulse for further transmission via the auditory nerve. The auditory nerve encodes the acoustic sounds that are conveyed to the auditory brainstem. Multiple brainstem nuclei, the cochlea, the midbrain, the thalamus, and the cortex constitute the central auditory system. In clinical practice, auditory brainstem responses (ABRs) to simple stimuli such as click or tones are widely used. Recently, complex stimuli or complex auditory brain responses (cABRs), such as monosyllabic speech stimuli and music, are being used as a tool to study the brainstem processing of speech sounds. We have used the classic ‘click’ as well as, for the first time, the artificial successive complex stimuli ‘ba’, which constitutes the Greek word ‘baba’ corresponding to the English ‘daddy’.

Patients and methods

Twenty young adults institutionally diagnosed as dyslexic (10 subjects) or light dyslexic (10 subjects) comprised the diseased group. Twenty sex-, age-, education-, hearing sensitivity-, and IQ-matched normal subjects comprised the control group. Measurements included the absolute latencies of waves I through V, the interpeak latencies elicited by the classical acoustic click, the negative peak latencies of A and C waves, as well as the interpeak latencies of A–C elicited by the verbal stimulus ‘baba’ created on a digital speech synthesizer.

Results

The absolute peak latencies of waves I, III, and V in response to monoaural rarefaction clicks as well as the interpeak latencies I–III, III–V, and I–V in the dyslexic subjects, although increased in comparison with normal subjects, did not reach the level of a significant difference (p < 0.05). However, the absolute peak latencies of the negative wave C and the interpeak latencies of A–C elicited by verbal stimuli were found to be increased in the dyslexic group in comparison with the control group (p = 0.0004 and p = 0.045, respectively). In the subgroup consisting of 10 patients suffering from ‘other learning disabilities’ and who were characterized as with ‘light’ dyslexia according to dyslexia tests, no significant delays were found in peak latencies A and C and interpeak latencies A–C in comparison with the control group.

Conclusions

Acoustic representation of a speech sound and, in particular, the disyllabic word ‘baba’ was found to be abnormal, as low as the auditory brainstem. Because ABRs mature in early life, this can help to identify subjects with acoustically based learning problems and apply early intervention, rehabilitation, and treatment. Further studies and more experience with more patients and pathological conditions such as plasticity of the auditory system, cochlear implants, hearing aids, presbycusis, or acoustic neuropathy are necessary until this type of testing is ready for clinical application.     

Auditory processing disorders: Relationship to cognitive processes and underlying auditory neural integrity

Background

Auditory processing disorder (APD) in children has been reported and discussed in the clinical and research literature for many years yet there remains poor agreement on diagnostic criteria, the relationship between APD and cognitive skills, and the importance of assessing underlying neural integrity.

Purpose

The present study used a repeated measures design to examine the relationship between a clinical APD diagnosis achieved with behavioral tests used in many clinics, cognitive abilities measured with standardized tests of intelligence, academic achievement, language, phonology, memory and attention and measures of auditory neural integrity as measured with acoustic reflex thresholds and auditory brainstem responses.

Method

Participants were 63 children, 7–17 years of age, who reported listening difficulties in spite of normal hearing thresholds. Parents/guardians completed surveys about the child's auditory and attention behavior while children completed an audiologic examination that included 5 behavioral tests of auditory processing ability. Standardized tests that examined intelligence, academic achievement, language, phonology, memory and attention, and objective tests auditory function included crossed and uncrossed acoustic reflex thresholds and auditory brainstem responses (ABR) were also administered to each child.

Results

Forty of the children received an APD diagnosis based on the 5 behavioral tests and 23 did not. The groups of children performed similarly on intelligence measures but the children with an APD diagnosis tended to perform more poorly on other cognitive measures. Auditory brainstem responses and acoustic reflex thresholds were often abnormal in both groups of children.

Summary

Results of this study suggest that a purely behavioral test battery may be insufficient to accurately identify all children with auditory processing disorders. Physiologic test measures, including acoustic reflex and auditory brainstem response tests, are important indicators of auditory function and may be the only indication of a problem. The results also suggest that performance on behavioral APD tests may be strongly influenced by the child's language levels.